Vision loss early in life has dramatic consequences on the organization of the visual system and hence on structural plasticity of its remnant components. Most of the studies on the anatomical changes in the brain following visual deprivation have focused on the re-organization of the visual cortex and its afferent and efferent projections. In this study, we performed a quantitative analysis of the volume and size of the optic chiasm, optic nerve, optic tract and the lateral geniculate nucleus (LGN), the retino recipient thalamic nucleus. Analysis was carried out on structural T1-weighted MRIs from 22 congenitally blind (CB), 14 late blind (LB) and 29 age -and sex-matched sighted control (SC) subjects. We manually segmented the optic nerve, optic chiasm and optic tract, while LGN volumes were extracted using in-house software. We also measured voxel intensity of optic nerve, optic chiasm and optic tract. Mean volumes of the optic nerve, optic tract and optic chiasm were reduced by 50 to 60% in both CB and LB participants. No significant differences were found between the congenitally and late-onset blind participants for any of the measures. Our data further revealed reduced white matter voxel intensities in optic nerve, optic chiasm and optic tract in blind compared to sighted participants, suggesting decreased myelin content in the atrophied white matter. The LGN was reduced by 50% and 44% in CB and LB, respectively. In LB, optic nerve volume correlated negatively with the blindness duration index; no such correlation was found for optic chiasm, optic tract and LGN. The observation that despite the absence of visual input about half of the subcortical retinofugal projections are structurally preserved raises the question of their functional role. One possibility is that the surviving fibers play a role in the maintenance of circadian rhythms in the blind through the intrinsically photosensitive melanopsin-containing retinal ganglion cells.

生命早期的视力丧失会对视觉系统的组织产生重大影响，从而影响其残余成分的结构可塑性。大多数关于视觉剥夺后大脑解剖变化的研究都集中在视觉皮层的重组及其传入和传出投射上。在这项研究中，我们对视交叉、视神经、视束和外侧膝状体核 (LGN)、视网膜受体丘脑核的体积和大小进行了定量分析。对 22 名先天性失明 (CB)、14 名晚期失明 (LB) 和 29 名年龄和性别匹配的视力正常对照 (SC) 受试者的结构 T1 加权 MRI 进行了分析。我们手动分割视神经、视交叉和视束，同时使用内部软件提取 LGN 体积。我们还测量了视神经、视交叉和视束的体素强度。CB 和 LB 参与者的视神经、视束和视交叉的平均体积减少了 50% 至 60%。对于任何测量，先天性和迟发性失明参与者之间没有发现显着差异。我们的数据进一步显示，与有视力的参与者相比，盲人视神经、视交叉和视束的白质体素强度降低，表明萎缩的白质中髓磷脂含量降低。CB 和 LB 的 LGN 分别降低了 50% 和 44%。在 LB 中，视神经体积与失明持续时间指数呈负相关；视交叉、视束和 LGN 没有发现这种相关性。尽管没有视觉输入，但大约一半的皮层下视网膜投射在结构上得到保留，这一观察提出了它们的功能作用的问题。一种可能性是，存活的纤维通过固有的光敏性含有黑视蛋白的视网膜神经节细胞在维持盲人的昼夜节律方面发挥作用。